Programming language and runtime environment that allows compiled Java programs to run unchanged on most hardware and software platforms

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58
votes
9answers
150k views

Can't seem to disable Java Automatic Update

I'm just tweaking out my new Windows 7 laptop and wanted to disable the automatic Java updating (and thus kill the silly jusched.exe background process), but I can't seem to get it to actually turn it ...
48
votes
7answers
61k views

How to determine JAVA_HOME on Debian/Ubuntu?

On Ubuntu it is possible to have multiple JVMs at the same time. The default one is selected with update-alternatives. But this does not set the JAVA_HOME environment variable, due to a debian policy. ...
25
votes
9answers
4k views

Is it a Best Industry practice to restart web servers periodically? [closed]

We have a web application (developed by a third party) that runs on Tomcat. We have been getting very bad performance from the application. The application developer is claiming that it is an ...
25
votes
5answers
56k views

Practical maximum open file descriptors (ulimit -n) for a high volume system

We recently began load testing our application and noticed that it ran out of file descriptors after about 24 hours. We are running RHEL 5 on a Dell 1955: CPU: 2 x Dual Core 2.66GHz 4MB 5150 / ...
23
votes
4answers
73k views

Where to set java heap options (e.g. -Xmx) for Tomcat 6 under Ubuntu 9.04?

I'm running Tomcat using the tomcat6 package from Ubuntu 9.04, which makes a daemon out of Tomcat using jsvc. I'd like to know the proper way to set Java heap options like -Xmx for Tomcat. I'd like to ...
20
votes
5answers
54k views

Top - what does Virtual memory size mean? …linux/ubuntu

I am running top to monitor my server performance and 2 of my java processes show virtual memory of up to 800MB-1GB. Is that a bad thing? What does virtual memory mean? And oh btw, I have swap of ...
16
votes
3answers
12k views

How do you manage Java in your Windows/Active Directory environment?

Like I suppose a lot of people, we have a Windows/Active Directory environment and a lot of internal line of business apps that require Java. Our experience is that Java does not play nice in such a ...
12
votes
5answers
47k views

What is the value of JAVA_HOME for CentOS?

I have install java through yum on CentOS, however another java programme needs to know what the JAVA_HOME environmental variable is. I know all about setting environmental variables, but what do I ...
12
votes
5answers
5k views

I'm designing a system to handle 10000 TCP connections per second, what problems will I run into?

I have a relatively new 8-core box running CentOS. I would like to develop a stats server that uses TCP. It's very simple, it accepts a TCP connection, increments a counter and closes the connection. ...
10
votes
6answers
8k views

Open source tomcat log viewer

I'm managing several tomcat instances (aprox 30-35) and looking for some console to centralize the logs. I tried php-syslog-ng before (no with tomcat), and found it useful. I would like that these ...
9
votes
2answers
693 views

How do you get the latest update for Java 6?

An application my company is considering buying requires Java 6. I am concerned that this is quite out of date and am recommending against the application as a result. But it seems that Oracle do ...
9
votes
5answers
644 views

How do I find the cause for a huge difference in performance between two identical Ubuntu servers?

I am running two Dell R410 servers in the same rack of a data center (behind a load balancer). Both have the same hardware configuration, run Ubuntu 10.4, have the same packages installed and run the ...
9
votes
4answers
2k views

JVM Memory Consumption

I am trying to run tomcat on a low memory system (150-256Mb). Even though I start the JVM with -Xmx64m (which should be the default anyway), the process immediately takes up 200Mb+. I wonder why the ...
9
votes
1answer
13k views

How can I restrict the java plugin to run only on certain sites in Internet Explorer?

I want to secure our centrally managed computers better and it is very difficult to automatically deploy the java runtime, but how to do that is another question. I find the security of Java ...
8
votes
4answers
2k views

is it possible to install java without the browser plugin?

I need java, but I don't want any browser to be able to access it. Is it possible to remove the whole applet/browser plugin code?
8
votes
4answers
15k views

Cannot switch, ssh to specific user: su: cannot set user id: Resource temporarily unavailable?

/var/log/secure: su: pam_keyinit(su-l:session): Unable to change UID to 500 temporarily su: pam_keyinit(su-l:session): Unable to change UID to 500 temporarily su: pam_unix(su-l:session): session ...
8
votes
5answers
3k views

Suggestions for free/cheap asset/patch management software (Adobe, Java, etc)

I am using WSUS for Microsoft patching but would like something that will inventory and patch Adobe, Java, Firefox, Quicktime, etc. I have used Lumension in the past and it was OK but it is too ...
8
votes
1answer
1k views

Tomcat: possible to exclude jars during app deployment?

By default, Tomcat prevents webapps from loading several .jars which are part of the Tomcat distribution (eg the servlet and JSP APIs) - is it possible to configure others to also be excluded? If it ...
7
votes
2answers
5k views

SSL Certificate Error: certificate_unknown

I want to create push notification server and while installing SSL certificate and .p12 file in server we are facing the below error: I want to know what is the wrong with ssl certificate because I am ...
7
votes
5answers
13k views

Tomcat 6.0 service does not start: java/lang/NoClassDefFoundError

I installed Tomcat on my Windows server but I can't get it to start. I start the service and I see the progress bar, but it fails. I installed the Java Runtime Environment Version 6 and created ...
7
votes
3answers
5k views

Sending email using SMTP (Gmail) from Hudson CI

How can I set up Hudson CI so that I can send out emails from the server following a build failure? At the moment all I get is the following error: com.sun.mail.smtp.SMTPSendFailedException: 530 ...
7
votes
1answer
49k views

Differences between classes12.jar, ojdbc14.jar, ojdbc5.jar and ojdbc6.jar

We are planning to upgrade our application servers to a new version of JRun which is carrying with it an upgrade from Java 1.4 to Java 1.6. As part of that, we have been testing various pieces of our ...
7
votes
3answers
21k views

How to get a linux network log?

We have a java server running in linux at a specific port that accepts persistent connections for thousands and thousands of users. Recently our clients are not able to connect with a time out error. ...
7
votes
1answer
10k views

How can I block Java updates, network-wide?

Java is constantly prompting users to upgrade and, when they do, it tries to install all sorts of other things which we must uninstall. Lately it installs a backup program called Carbonite. We’ve ...
6
votes
6answers
9k views

How to block access to a file from being served by Tomcat?

We have a few tomcat servers and we just discovered that some files that we don't want public to have access to those files. To exemplify: Let say we have a folder /var/www/html/ that we are ...
6
votes
4answers
183 views

Crashing my disk using Java

I have a Java program that must do the following 3 things: Download a file from a website. Run the file trough testA and testB (both in java) Delete the file and save the test results on the disk. ...
6
votes
5answers
3k views

OpenJDK vs. Sun Java6 on Ubuntu

Due to past (bad) experience resulting from the GCJ stuff being provided by default on certain distributions, I've always traditionally installed the official Sun Java package on servers. On Ubuntu ...
6
votes
8answers
3k views

Deployment and monitoring tools for java/tomcat/linux environment

I'm a developer for many years, but don't have tons of experience in ops, so apology if this is a newbe question. In my company we run a web service written in Java mainly based on a Tomcat web ...
6
votes
4answers
7k views

which JVM is best for Tomcat?

I have Tomcat 6.0 up and running. I went to tweak the memory sizes and realized that I have it running on the Sun JDK 1.6 client JVM. I don't have the Sun server JVM installed: C:\>java -client ...
6
votes
5answers
1k views

Cannot create Java VM on OpenVZ

I'm constantly encountering an error related to Java and certificates on my Ubuntu server running in OpenVZ when installing things from apt-get. I'm pretty sure it has to do with how Java allocates ...
6
votes
2answers
337 views

SSH unresponsive after stopping Tomcat, many ksoftirqd CPU usage

I have a weird issue. Every time I stop Tomcat, SSH becomes very slow, almost totally unresponsive. It takes a minute or even more for SSH to accept any command. When I finally get Tomcat started ...
6
votes
1answer
2k views

Tomcat Excessive Memory Consumption

I have a fresh server running Ubuntu 11.04 (Natty) (64-bit). I started off by installing openjdk and tomcat6. When the Tomcat server starts up, it immediately uses 480+ MB of memory. This seems way ...
6
votes
1answer
2k views

Tomcat7 PPA for Ubuntu LTS 10.04.2

Does anyone know of a ppa / repo that will install tomcat7. I know I can install from source but I'd rather if possible use a PPA/Repo. I found a nice one for sun*cough*oracle-java but there does ...
5
votes
8answers
13k views

Run Jar in Background on Linux

I have a jar that runs forever (infinite loop with socket listening thread) and need it to run in the background at all times. An example would be: "java -jar test.jar" How do I do this? Thanks in ...
5
votes
5answers
10k views

How can I monitor memory usage for a windows-based JVM and trigger an alert if it gets too high?

I have an app that runs as a JVM in Windows 2008. I'd like to monitor it's memory usage and be sent an email if/when memory usage reaches a specific threshold. Is there a free utility or method for ...
5
votes
5answers
7k views

How to reliably take Java Heap Dumps?

My team is running into difficulties when trying to take good heap dumps triggered by OutOfMemoryErrors. For specific reasons we are currently taking the dumps with jmap called from a bash script ...
5
votes
2answers
2k views

PermGen error in Java, while memory usage seems low

Java application dies from time to time with PermGen space error, but when I look at the memory usage it seems low from what I can tell. It is a Tomcat application, plus there is SOLR server running ...
5
votes
2answers
2k views

Can I host my web application in Cloud?

I have made a small web application created in J2EE which i want to develop as a "business". Can i host it in one of the cloud services ? Please do advice me as well on this issue. Will the cloud ...
5
votes
2answers
9k views

How to prevent slow responding Tomcat from making Apache slow to respond?

I have a site that consists mostly of static html pages with occasional ajax requests. The site is running on Apache, ajax is handled by Tomcat. If Tomcat becomes slow to respond (java cannot connect ...
5
votes
3answers
770 views

Scripted install of Sun Java JDK on Ubuntu 9.04

We are trying to script the install of the sun jdk on Ubuntu 9.04 and have it automatically accept the license agreement. I have seen something around the net about creating a file that the package ...
5
votes
2answers
3k views

Using both basic and client-certificate authentication with GlassFish

I'm currently building a Java-servlet applcation (using Jersey on GlassFish to be specific). In some parts of the application I need to authenticate the user using basic authentication and in some ...
5
votes
4answers
211 views

What issues do you need to check for deploying a java application on linux?

What issues should be specifically checked for when deploying a server application written in Java (without any specific platform dependencies) that was written and tested on Windows. Two that I know ...
5
votes
5answers
998 views

What configuration changes do you make to a new Tomcat installation?

After installing Tomcat 5 what configuration changes/tweaks do you apply, and why? Be specific: name what files you edit, what settings you change and why you do it. Some areas of interest: ...
5
votes
3answers
736 views

Virtualbox HTTP load testing, host CPU overload issues

I'm doing HTTP load testing benchmarks (using Apache Benchmark and Siege) on a small Java EE 1.7.0 / Tomcat 7.0.26 application running on a Debian Squeeze 6.0.4 x64 virtualized with Virtualbox 4.1.8. ...
5
votes
2answers
8k views

what is .crt and .key and how can I generate them?

SSLEngine on SSLCertificateFile /etc/httpd/conf/login.domain.com.crt SSLCertificateKeyFile /etc/httpd/conf/login.domain.com.key SSLCipherSuite ALL:-ADH:+HIGH:+MEDIUM:-LOW:-SSLv2:-EXP ...
5
votes
1answer
435 views

“runas” or “sudo” equivalent on AS400 IBM iSeries

I'm trying to invoke a program to run as another user (by getting input user/pwd) in AS400 OS using Java. Like runas in Windows or sudo in Unix — what can we do in AS400 OS? I am able to invoke basic ...
4
votes
3answers
324 views

MultiCPU servers - which one can you suggest? [closed]

We want to install a couple of big servers for our customer to run Oracle on one and Java applications on another. Tired with clusters, replications, want to run everything on one big server. We ...
4
votes
8answers
323 views

What platform do you run your java apps on?

Even though the JVM is cross-platform, there are be differences in behaviour; performance; stability. Some of them are quite clear, as in the heap size limitation on 32bit. Some of them are not, ...
4
votes
3answers
214 views

Java default JRE parameters on Unix

Is it possible to configure java in unix to always add a JRE parameter whenever java is run? e.g. -Dcom.sun.management.jmxremote.port=25800
4
votes
3answers
196 views

Why shouldn't I serve my Java webapp directly with Tomcat?

I have heard several times that one should not serve a Java webapp directly to the outside world from the Tomcat server it is running on. Rather, one should have a regular web server in between -- ...